The present invention relates to a laser spot welder for use with a manipulator mechanism such as an industrial robot.
It is generally known that conventional electric spot welders are used in conjunction with industrial robots for processing work on automotive assembly lines. Such spot welders are generally connected to the manipulatable end effector of the robot and are movable to perform a variety of welding tasks.
Conventional electric spot welders are constructed as follows: A pair of opposing copper tips are movable between open and closed positions with respect to one another so that they may tightly clamp a workpiece between the tips. The welding guns as they are referred to, have an electrode force clamping package in the neighborhood from 600 to 1500 lbs. to be exerted against the workpiece. High amperage current is then passed through the electrode pair causing resistance welding to occur at the build up of heat at the interface of two layers of weldable material. The electrode and clamping mechanism is fitted with a cooling water line to remove the heat from the welding tool.
Many disadvantages are associated with conventional electric resistance spot welding guns. For example: the high mechanical clamping forces causes deformation of the relatively soft copper electrode over a period of time; similarly, an indentation is caused on the sides of the workpiece during welding; the high temperature of the electrode tips causes a gradual burning and degradation of the electrode tip; the electrode tips must be periodically redressed to present a shiny and properly shaped end to the workpiece; and, the electrodes must periodically be replaced.
When conventional electric resistance spot welding guns are employed at stationary work stations, the power supply and related connections do not present a problem. However, when used in conjunction with the movable end of a robot, the difficulty of moving the end package and its associated connections becomes of paramount importance. The conventional spot welding gun requires a transformer to be carried with the robot and heavy copper wires to be connected from the transformer to the welding gun. These wires as well as the water cooling hoses cause additional weight to be borne by the industrial robot. Additionally, the wiring package is usually not very flexible, and thus the robot will be faced with mechanical drag and resistance when performing its programmed moves.
It has been proposed to employ lasers in conjunction with industrial robots to perform a variety of tasks previously done with conventional tools. For example, industrial robots have utilized a laser beam to cut and trim workpieces. Such laser beams may typically emanate from a CO.sub.2 light source, and a problem encountered is that the laser generating unit such as a 1.5 KW "power laser" to perform work on industrial workpieces may weigh in the order of 350 to 550 lbs. Therefore, it has been proposed that the light source be located somewhat remote from the robot unit and the light beam be directed through an articulatable conduit having a flexible arm structure with totally reflecting mirror positioned in its articulation joints, such as might be used in laser surgery. At the end of the system, the laser beam is focused to a small spot by a focusing lens provided in the end of the light conducting mechanism. The focusing lens unit is typically connected in some fashion to the end effector of a robot, so that the robot may perform its programmed moves and need only be concerned with carrying the output end of the laser conducting mechanism.
It has been proposed that a laser beam source be used for welding operations. In consideration of a spot welding operation, two layers of a weldable material must be intimately placed in contact with one another and a laser beam directed at at least one surface of the layered assembly. Sufficient heat is generated by a power laser to cause an interface melting of the two materials and a consequent weld formation between the two. It would seemingly be a relatively simple task to therefore perform spot welding operations utilizing a laser beam in industrial applications by simply focusing the beam at a desired number of spots on material to be welded. However, in practical application, the task of performing production spot welding intervals is a difficult one for the reason that the workpieces generally are not totally flat and therefore, are not in intimate contact with one another. Mechanical misalignments of components to be welded, and slight deformations and tolerance variations may cause the weldable materials to be slightly spaced apart at the weld site.
Applicant has obviated the difficulties inherent in the prior art devices by a novel laser spot welding unit which is suitable for portable manipulation by an industrial robot. Further, the novel device will permit the weldable workpieces to be placed in intimate contact with one another with relative ease and without obstructing the path of the laser beam.
It is therefore an object of the present invention to provide a laser spot welder which may be easily employed on the end effector of an industrial robot.
Another object of the present invention is to provide a laser spot welder with integral part holding means for maintaining weldable workpieces in intimate contact with one another.
Another object of the present invention is to provide a laser spot welder for use with an industrial robot wherein workpiece holding means is employed which will permit an unobstructed path for the laser welding beam.